<i>While we're talking churches I just want to slip one in. There are many tales about holy wells that tell of monks striking the ground and water sprouting forth. Were they just very good dowsers?</i>

Could well be <g>

It's also possible their staffs acted as a "listening stick".

The Water Board still use these to find leaks in the mains water supply.( They thought there was a leak somewhere on my drive, that's how I found out about it.) The stick itself is like a straight walking-stick but the top end is wider than the bottom and chopped off flat. Basically, you put the thin end of the stick on the ground and listen to the thicker end. You can clearly hear running water. I was fascinated as I'd not seen anything like this before but apparrently "listening sticks" are in common use particularly in engineering for tuning engines.

If the monks' staffs were shaped correctly*, then they could have easily located a source of underground water. I'd guess after a little practise, you could tell how close the water that you could hear was to the surface.

* I've not had a go with anything other than the purpose made one that the guy from the Water Board was using, but it's possible some wood is better at transmitting the sound than others. Also, I don't know if listening sticks go by any other name, that's what the Water Board Guy called it.